The superior performance of Nb-modified Cu-Ce-Ti mixed oxides for the selective catalytic reduction of NO with NH3 at low temperature

In this paper, a series of Nb modified Cu-Ce-Ti mixed oxides (NbyCCT) were synthesized using wetness impregnation method for the selective catalytic reduction of NO with ammonia (NH3-SCR). The activity tests indicated that NbyCCT catalysts had shown superior SCR performances. Among which, Nb0.0.5CCT catalyst exhibited a NO conversion of more than 90% within a broad operation temperature window (180-360 degrees C) under the GHSV of 40,000 h(-1). After that, corresponding characterizations were performed to correlate the physical structures and surface properties to catalytic performances. These results revealed that the strong interactions among the active phases induced by Nb addition could not only enhance the redox property of the catalysts but also inhibit the over-oxidation of NH3, which would be beneficial to SCR performance within a wide temperature range and good reaction selectivity. Furthermore, DRIFTS results suggested that the doping of Nb could promote the formation of NO2, thereby enhancing the "fast" SCR reaction process (Langmuir-Hinshelwood reaction pathway). Moreover, the Nb0.05CCT catalyst showed a better sulfur tolerance compared to Nb free catalyst that over 85% NO conversion could be retained after 12 h SCR reaction in the presence of SO2 and H2O.